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Absorbers - What do these scores actually mean, in multi-layer simulations?

73hadd

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Question for those familiar with absorption performance scores. I have read that 1=total absorption. What is the real, if measurable or perceived, difference between a .9 and a .95 for example?

Using this tool:


absorb.jpg


I have run a few sims and found a few solutions that I like.

The blue line is a 12" absorber based on 3 layers of different material, 100mm each. I decided to try and model this based on the idea that going from lightest-densest would have the least reflection. As you can see it is very smooth down to 200hz.

The green line is a 12" absorber which would be 300mm one material. It is not quite as smooth but extends a bit more. The main difference is around 400hz where the multi-material absorber is flatter, with the green line down about .05. What is likely to be the measured performance difference? The advantage being it's simpler to use more of the same material.

Thanks to @Frgirard for posting about the 50cm of 5000 as that looks like a really useful absorber. Shown as the red line, it is not as flat down to 200hz but has good extension.

The orange line is from https://www.don-audio.com/Acoustic-room-treatment-guide. Used separately, it covers 100hz well and .8 at 60hz. It has big dips so it doesn't look good by itself for broadband. Used with one of the 12" options it woud be good coverage.

I am used to thinking about this like frequency response and want to see a flat line. But maybe for absorption anything above .8 or maybe even .6, is effective enough?

Yes, I am ignoring all of the "what size room" and "where to place them" background. I know that these concepts are important in application, but at this point I am only interested in the exercise of planning something broadband with good extension.

Also, this is specific to these densities and materials as I want to use something like Caruso or Basotect, and stay away from Fiberglass or Mineral wool.

Thanks @abdo123 for mentioning that Basotect is 12400. I have not been able to source it in the US.
 
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abdo123

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I think you're focusing too much on the values, I appreciate the red line the most because it rolls off slowly. But you should really focus the most on getting as much surface area in the room covered, while keeping the air flow resistivity of the material appropriate for the thickness that you're going to use.

If you're going to cover up large percentage of room surface (20%+) with the orange one, I'm concerned that you might color the sound of your room as it absorbs frequencies unevenly.
 
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